MOTM

Hey all!

Here's one for the troubleshooting crowd - my power supply is doing a 
*funny* thing.  Back when module #38 was installed, I switched on the 
power and only the red LED's lit and stayed on solid-no modulation 
from the LFO's, etc.  Naturally, I switched the supply off!  When I 
got the courage to power it up again, all was well.  Or so I 
thought...

Yesterday I installed module #44.  A new distribution board was added 
and the wiring was rearanged to tidy up.  I powered up and this time 
the green LED's lit solid.  I turned it off and then back on.  Now 
the red LED's lit solid!  I left it like this to confirm what I 
thought was happening.  Checking the voltages at my DC terminals on 
the supply, I found a solid -15vdc and only +.71vdc.  When the green 
LED's lit solid, the opposite was true- solid positive voltage and 
only -.71vdc from the supply.

When the supply powers up normally, all works well.  The voltages at 
any module show no sign of brownout.  With no load, the supply always 
powers up correctly.  I haven't pulled one supply at a time to find 
an offending module, because the odds are against any one module 
shorting one-or-the-other half of the supply.  That is next on the 
agenda, however.  The supply is a Power One HBB-15 which according to 
many, *should* handle 45-50 modules.  A star wiring pattern has been 
maintained, and the three distribution boards are MOTM-960's. The DC 
wiring is 12-guage stranded from the supply to the first terminal and 
12-guage to each distribution board.

What do you think?  My guess is the power supply goes into short 
protection during inrush.  The .71 vdc would be a normal forward 
voltage drop from the pass transistor, showing up in parallel at the 
shut-down side of the supply.  Anyone else, have something like this 
happen as they neared the limits of power?  Am I just going to pop 
for the next bigger (or greater!) supply?  

I summon the vast power of knowledge that is the MOTM Group!

Chub - half-powered!

ps-Paul should really go into cartooning!

A really simple question:  Did you recheck all of your power 
connections?  I got one wrong once and while it didn't fry any modules, I 
did have some LEDs light solid (I think it was a 320 LFO that did 
that).  Anyway, it is always worthwhile to check your power connectors.  It 
is easy to get those off by one peg.

I also wonder with 44 modules you must have one hellova power supply to run 
them.  You might want to do the math on your module load vs. your power 
supply.  It might be time for another.

         Eric (who just received his 950 power supply just minutes ago!)


At 10:59 AM 12/27/2003 -0600, J. Larry Hendry wrote:

>I've often wondered if we were taxing the short circuit power-p current of
>these power supplies with the all the caps we put on these modules.  Every
>module has at least a 10 uF to 22uF cap on each power leg.  That could
>easily reach ~ 500uF on top of the caps in the supply.  A cap does indeed
>look like a short circuit when power is first applied.  Some modules have
>lots more.  And, some modules, like the Blacet Time Machine and others draw
>a lot more normal current.  38 of those would way overload a supply like.
>But, who would have 38 Time Machines. :)  Perhaps someone trying to impress
>list-lurker Harry with his collection of BDDs. :)
>Larry H
>
>----- Original Message -----
>From: charlesosthelder <osthelder@...>
>To: <motm@yahoogroups.com>
>Sent: Saturday, December 27, 2003 8:40 AM
>Subject: [motm] power anomoly
>
>
>Hey all!
>
>Here's one for the troubleshooting crowd - my power supply is doing a
>*funny* thing.  Back when module #38 was installed, I switched on the
>power and only the red LED's lit and stayed on solid-no modulation
>from the LFO's, etc.  Naturally, I switched the supply off!  When I
>got the courage to power it up again, all was well.  Or so I
>thought...
>
>Yesterday I installed module #44.  A new distribution board was added
>and the wiring was rearanged to tidy up.  I powered up and this time
>the green LED's lit solid.  I turned it off and then back on.  Now
>the red LED's lit solid!  I left it like this to confirm what I
>thought was happening.  Checking the voltages at my DC terminals on
>the supply, I found a solid -15vdc and only +.71vdc.  When the green
>LED's lit solid, the opposite was true- solid positive voltage and
>only -.71vdc from the supply.
>
>When the supply powers up normally, all works well.  The voltages at
>any module show no sign of brownout.  With no load, the supply always
>powers up correctly.  I haven't pulled one supply at a time to find
>an offending module, because the odds are against any one module
>shorting one-or-the-other half of the supply.  That is next on the
>agenda, however.  The supply is a Power One HBB-15 which according to
>many, *should* handle 45-50 modules.  A star wiring pattern has been
>maintained, and the three distribution boards are MOTM-960's. The DC
>wiring is 12-guage stranded from the supply to the first terminal and
>12-guage to each distribution board.
>
>What do you think?  My guess is the power supply goes into short
>protection during inrush.  The .71 vdc would be a normal forward
>voltage drop from the pass transistor, showing up in parallel at the
>shut-down side of the supply.  Anyone else, have something like this
>happen as they neared the limits of power?  Am I just going to pop
>for the next bigger (or greater!) supply?
>
>I summon the vast power of knowledge that is the MOTM Group!
>
>Chub - half-powered!
>
>ps-Paul should really go into cartooning!
>
>
>
>
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Indeed.

I have experienced the same thing when powering too many modules from a 
900. One power rail drops and all the modules freak out. It didn't seem to 
cause any damage, but it did freak me out too. Then it would start up again ok 
if I cycled the power.

I haven't had any problems since I swapped in a much larger supply.

Max


--- In motm@yahoogroups.com, "charlesosthelder" <osthelder@n...> wrote:
.....

> 
> What do you think?  My guess is the power supply goes into short 
> protection during inrush.  The .71 vdc would be a normal forward 
> voltage drop from the pass transistor, showing up in parallel at the 
> shut-down side of the supply.  Anyone else, have something like this 
> happen as they neared the limits of power?  Am I just going to pop 
> for the next bigger (or greater!) supply?  
>

I've often wondered if we were taxing the short circuit power-p current of
these power supplies with the all the caps we put on these modules.  Every
module has at least a 10 uF to 22uF cap on each power leg.  That could
easily reach ~ 500uF on top of the caps in the supply.  A cap does indeed
look like a short circuit when power is first applied.  Some modules have
lots more.  And, some modules, like the Blacet Time Machine and others draw
a lot more normal current.  38 of those would way overload a supply like.
But, who would have 38 Time Machines. :)  Perhaps someone trying to impress
list-lurker Harry with his collection of BDDs. :)
Larry H

----- Original Message -----
From: charlesosthelder <osthelder@...>
To: <motm@yahoogroups.com>
Sent: Saturday, December 27, 2003 8:40 AM
Subject: [motm] power anomoly


Hey all!

Here's one for the troubleshooting crowd - my power supply is doing a
*funny* thing.  Back when module #38 was installed, I switched on the
power and only the red LED's lit and stayed on solid-no modulation
from the LFO's, etc.  Naturally, I switched the supply off!  When I
got the courage to power it up again, all was well.  Or so I
thought...

Yesterday I installed module #44.  A new distribution board was added
and the wiring was rearanged to tidy up.  I powered up and this time
the green LED's lit solid.  I turned it off and then back on.  Now
the red LED's lit solid!  I left it like this to confirm what I
thought was happening.  Checking the voltages at my DC terminals on
the supply, I found a solid -15vdc and only +.71vdc.  When the green
LED's lit solid, the opposite was true- solid positive voltage and
only -.71vdc from the supply.

When the supply powers up normally, all works well.  The voltages at
any module show no sign of brownout.  With no load, the supply always
powers up correctly.  I haven't pulled one supply at a time to find
an offending module, because the odds are against any one module
shorting one-or-the-other half of the supply.  That is next on the
agenda, however.  The supply is a Power One HBB-15 which according to
many, *should* handle 45-50 modules.  A star wiring pattern has been
maintained, and the three distribution boards are MOTM-960's. The DC
wiring is 12-guage stranded from the supply to the first terminal and
12-guage to each distribution board.

What do you think?  My guess is the power supply goes into short
protection during inrush.  The .71 vdc would be a normal forward
voltage drop from the pass transistor, showing up in parallel at the
shut-down side of the supply.  Anyone else, have something like this
happen as they neared the limits of power?  Am I just going to pop
for the next bigger (or greater!) supply?

I summon the vast power of knowledge that is the MOTM Group!

Chub - half-powered!

ps-Paul should really go into cartooning!




Yahoo! Groups Links

To visit your group on the web, go to:
 http://groups.yahoo.com/group/motm/

To unsubscribe from this group, send an email to:
 motm-unsubscribe@yahoogroups.com

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 http://docs.yahoo.com/info/terms/

>What do you think?  My guess is the power supply goes into short
>protection during inrush.  The .71 vdc would be a normal forward
>voltage drop from the pass transistor, showing up in parallel at the
>shut-down side of the supply.  Anyone else, have something like this
>happen as they neared the limits of power?  Am I just going to pop
>for the next bigger (or greater!) supply?
>
>I summon the vast power of knowledge that is the MOTM Group!

This happens to me too. I have 6 cabinets, each with their own 900 
power supply. One of the cabinets will occasionally start up with the 
-15V line brain dead. This is immediately obvious because the 320s 
don't oscillate anymore (the LEDs stay lit at maximum green). I have 
to toggle the power to this cabinet a few times to get it to work 
properly. When it does start up properly, everything in that cabinet 
works fine. As you've noted, it looks like some kind of current surge 
at startup.

I rebuilt my cabinets recently and noticed that this problem went 
away completely when the number of modules in the cabinet was 
reduced. I can't pinpoint it to a specific module, only to the number 
of modules in the cabinet. As it stands now, if I remove power from 
any single module in that cabinet, the problem goes away entirely.

jlarryh@... writes:

> I've often wondered if we were taxing the short circuit power-p current of
>  these power supplies with the all the caps we put on these modules. 

 This is what I was thinking too. After upgrading to a Condor HCBB75W supply 
(1.5A each 15V rail) and having the previously mentioned power-on symptom, I 
slightly tweaked the current limit pot. The problem hasn't returned since. I'm 
running about 28 modules off of this supply.

 Andrew

As suggested in other emails, the start-up current is probably too great for
the supply. The solution is relatively simple. Power the modules in banks -
i.e. ten per switch, and turn them on one after the other.

Our office supply was like this - we'd happilly run on the one circuit
breaker until something overloaded it, then there was no way we could get
that breaker to close again due to all the in-rush currents of the
switchmode PSUs and degausing circuits. EVERYTHING had to be disconnected,
then added one unit at a time after the breaker was closed.

Ken

>Hey all!
>
>Here's one for the troubleshooting crowd - my power supply is doing a 
>*funny* thing.  Back when module #38 was installed, I switched on the 
>power and only the red LED's lit and stayed on solid-no modulation 
>from the LFO's, etc.  Naturally, I switched the supply off!  When I 
>got the courage to power it up again, all was well.  Or so I 
>thought...
_______________________________________________________________________
Ken Stone   sasami@...  
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Well group, Andrew wins this round of "Troubleshoot That Synth!".  He 
reminded me that the power supplies have a current limiter resistor 
in the form of a trimpot!

The Power One HBB-15 has two trimpots - one for each output of the 
supply - and they have taken the precaution of painting over the 
wiper shafts with anti-idiot lacquer.  This crumbles away easily with 
the tip of a small screwdriver or an x-acto blade.  I raised both to 
the maximum current.  This shouldn't cause any problems.  There is a 
resistor in series with the trimpot and the "over-current" condition 
being limited is very short duration.  Likewise, the current 
consumption of all the modules is well within the capability of the 3 
amp supply.  Not even breaking a sweat...

Now, even with the module count of the Engine of Chaos at 47, there 
is no more power anomoly.  World domination is now just within my 
grasp!!!

Thanks everyone!

Chub- drunk with power!